Unsafe firearm and cartridge combinations are combinations of firearms and cartridges which can cause an unsafe condition for the shooter when firing.

The unsafe condition can arise due to use of a cartridge intended for another chambering (see SAAMI list below), or using overpressure ammunition in a firearm not designed for such pressures, or using explosive (tampered) ammunition, or otherwise unsafe ammunition.

Another example of an unsafe firearm and cartridge combination is the firing of saboted rounds in firearms with muzzle devices (such as a flash suppressor, muzzle brake, or choke) unless the muzzle device has been specifically designed for safe use with that particular type of saboted ammunition (see Saboted ammunition and muzzle devices below).

SAAMI listing The U.S. based Sporting Arms and Ammunition Manufacturers' Institute (SAAMI) has listed a number of known unsafe firearm chamber and cartridge combinations which can happen due to mixing of different common cartridges.

Examples include:

Firing a .22 Long Rifle round in a .17 HMR rifle Firing a .357 Magnum round in a .38 Special revolver (the opposite is however is a safe and very common practice) Firing a 9×19 mm round in a .40 S&W pistol Firing a .300 Blackout round in a .223 Remington rifle Firing shotgun shell of the correct gauge or bore, but in a chamber length that is too short (for example a 70 mm shell in 65 mm chamber)

While the table below lists most unsafe combinations known by SAAMI, the list is not exhaustive of all dangerous combinations due to the large number of cartridges.

+SAAMI list of unsafe firearm chamber and cartridge combinationsFirearm chamberingUnsafe cartridge(s)RIMFIRE:5 mm Remington Rimfire Magnum.17 Precision Made Cartridge, .17 Mach 2, .22 BB Cap, .22 CB Cap, .22 Short, .22 Long, .22 Long Rifle, .22 Long Rifle Shot, .22 Winchester Automatic.17 Hornady Magnum Rimfire.17 Precision Made Cartridge, .17 Mach 2, .22 CB Short, .22 Short, .22 Long, .22 Long Rifle, .22 Stinger, .22 CB, .17 Hornady Magnum Rifle.17 Winchester Super Magnum.17 Hornady Magnum Rifle.17 Precision Made Cartridge.22 BB Cap.22 Short.17 Mach 2.22 Long.17 Mach 2.22 Winchester Rimfire.17 Precision Made Cartridge, .22 BB Cap, .22 CB Cap, .22 Short, .22 Long, .22 Long Rifle, .22 Long Rifle Shot.22 Winchester Magnum.17 Precision Made Cartridge, .22 BB Cap, .22 CB Cap, .22 Short, .22 Long, .22 Long Rifle, .22 Long Rifle Shot.22 Winchester Automatic.17 Precision Made Cartridge, .22 BB Cap, .22 CB Cap, .22 Short, .22 Long, .22 Long Rifle, .22 Long Rifle Shot.25 Stevens5 mm Remington RF MagnumCENTERFIRE SHOTGUN:10 gauge (19.7 mm)12 gauge (18.5 mm)12 gauge (18.5 mm)16 gauge (16.8 mm), 20 gauge (15.6 mm)16 gauge (16.8 mm)20 gauge (15.6 mm)20 gauge (15.6 mm)28 gauge (14.0 mm).410 bore (10.4 mm)Any centerfire metallic cartridgeCENTERFIRE HANDGUN:9×19 mm Luger9×19 mm NATO (Military), .40 S&W, 9×18 Makarov9 mm Winchester Magnum9×18 Makarov9×18 Makarov9×19 mm Luger, .38 Automatic, .38 Super Automatic +P, .380 Automatic9×23 mm Winchester.38 Super Automatic +P, .380 Automatic.32 H&R Magnum.32 Long Colt.32 Smith & Wesson.32 Automatic, .32 Long Colt, .32 Short Colt32-20 Winchester32-20 Winchester High Velocity.357 Sig9×19 mm Luger.38 Automatic.38 Super Automatic +P, 9×19 mm Luger, 9×18 mm Makarov, 9×23 mm Winchester.38 Super Automatic +P9×19 mm Luger, 9×18 Makarov, 9×23 Winchester.38 Smith & Wesson.38 Automatic, .38 Long Colt, .38 Short Colt, .38 Special, 9×18 Makarov.38 Special.357 Magnum, .380 Automatic.40 S&W9×19 mm Luger.44-40 Winchester.44-40 Winchester High Velocity.45 Automatic.38-40 Winchester, .44 Remington Magnum, .44 Special, .44-40 Winchester, .45 Glock Automatic Pistol.45 Colt.38-40 Winchester, .44 Remington Magnum, .44 Special, .44-40 Winchester, .454 Casull.45 Winchester Magnum.45 Automatic, .45 Glock Automatic Pistol, .454 Casull.45 Glock Automatic Pistol.45 Automatic, .45 Winchester Magnum.475 Linebaugh.45 Long Colt, .44 Remington Magnum, .44 S&W Special, .45 Automatic Rim.480 Ruger.45 Long Colt, .44 Remington Magnum, .44 S&W Special, .45 Automatic RimCENTERFIRE RIFLE:5.56×45 mm NATO.25-45 Sharps6 mm Remington (.244 Rem).250 Savage, 7.62×39 mm6.5 mm Remington Magnum.300 Savage6×47 mm Remington.25-45 Sharps6.5 mm Creedmoor.357 Magnum, .357 Remington Maximum6.5-06 A-Square7.62×39 mm6.5x55 mm7 mm BR Remington, 7.62×39 mm, .300 Savage6.5-284 Norma6 mm Creedmoor, 6.5 mm Creedmoor6.5-300 Weatherby Magnum.257 Weatherby Magnum, .270 Weatherby Magnum, 7 mm Weatherby Magnum, 7 mm Remington Magnum, .300 Winchester Magnum, .338 Winchester Magnum7 mm Express Remington7×57 mm, .270 Winchester, .30 Remington, .30-30 Winchester, .300 Savage, .308 Winchester, .32 Remington, .375 Winchester, .38-55 Winchester7×57 mm7.62×39 mm, .300 Savage, .30-30 Winchester7 mm Remington Magnum7 mm Express Remington, 7×57 mm, 7 mm Remington Ultra Magnum, 7 mm Weatherby Magnum, .270 Winchester, .280 Remington, .300 Winchester Magnum, .303 British, .308 Winchester, .35 Remington, .350 Remington Magnum, .375 Winchester, .38-55 Winchester7 mm Remington Short Action Ultra Magnum7 mm-08 Remington, .357 Remington Maximum, .454 Casull, .480 Ruger7 mm Remington Ultra Magnum.300 Winchester Magnum7 mm Shooting Times Westerner.30-06 Springfield, .30-40 Krag, .300 Winchester Magnum, .350 Remington7 mm Weatherby Magnum7 mm Express Remington, 7×57 mm, 7 mm Remington Magnum, 8×57 mm, .270 Winchester, .280 Remington, .303 British, .308 Winchester, .35 Remington, .350 Remington Magnum, .375 Winchester, .38-55 Winchester7 mm-08 Remington7.62×39 mm8×57 mm7×57 mm, .35 Remington8 mm Remington Magnum.338 Winchester Magnum, .350 Remington Magnum, .358 Norma Magnum, .375 Winchester, .38-55 Winchester.17 Remington.221 Remington Fireball, .25-45 Sharps, .30 Carbine, .300 AAC Blackout.17-223 Remington.17 Remington, .221 Remington Fireball, .30 Carbine.20 Nosler.221 Remington Fireball, .300 AAC Blackout.204 Ruger.25-45 Sharps.22-250 Remington.204 Ruger.22 Nosler.300 AAC Blackout.220 Swift7.62×39 mm.222 Remington.25-45 Sharps, .300 AAC Blackout.223 Remington5.56×45mm NATO, .222 Remington, 25-45 Sharps, .30 Carbine, .300 AAC Blackout.224 Weatherby Magnum.222 Remington Magnum.240 Weatherby Magnum.220 Swift, .225 Winchester.243 Winchester7.62×39 mm, .225 Winchester, .250 Savage, .300 Savage.243 Winchester Super Short Magnum.30 Carbine, .32-20 Winchester.25 Winchester Super Short Magnum.30 Carbine, .32-20 Winchester.25-06 Remington7 mm BR Remington, 7.62×39 mm, .308 Winchester.25-45 Sharps.300 AAC Blackout.257 Roberts7.62×39 mm, .250 Savage.257 Weatherby Magnum.25-06 Remington, .25-35 Winchester, 6.5 mm Remington Magnum, .284 Winchester, 7 mm-08 Remington, 7×57 mm, 7.62×39 mm, .300 Savage, .303 Savage, .307 Winchester, .308 Winchester, .30-30 Winchester, .32 Winchester, .32-40 Winchester, .35 Remington, .350 Remington Magnum, .356 Winchester, .358 Winchester, .375 Winchester, .38-55 Winchester.26 Nosler7 mm Remington Short Action Ultra Magnum, .30-30 Winchester.264 Winchester Magnum.270 Winchester, .284 Winchester, .303 British, .350 Remington, .375 Winchester, .38-55 Winchester.27 Nosler7 mm Remington Magnum, 30-30 Winchester.270 Weatherby Magnum.25-06 Remington, .270 Winchester, .280 Remington, .284 Winchester, 7 mm-08 Remington, 7-30 Waters, .30 Remington, .30-30 Winchester, .300 Savage, .303 Savage, .307 Winchester, .308 Winchester, .32 Winchester, .32 Winchester Special, .32-40 Winchester, .35 Remington, .35 Remington Magnum, .356 Winchester, .375 Winchester, .38-55 Winchester.270 Winchester7.62×39 mm, .30 Remington, .30-30 Winchester, .300 Savage, .308 Winchester, .32 Remington, .375 Winchester, .38-55 Winchester.270 Winchester Short Magnum7 mm Remington Short Action Ultra Magnum, .32-40 Winchester, .38-40 Winchester, .44-40 Winchester, .44 Remington Magnum, .45 Colt, .454 Casull, .480 Ruger.28 Nosler.30-30 Winchester.280 Remington7×57 mm, 7.62×39 mm, .270 Winchester, .30 Remington, .30-30 Winchester, .300 Savage, .308 Winchester, .32 Remington, .375 Winchester, .38-55 Winchester.284 Winchester7×57 mm, .300 Savage.30 Thompson Center.41 Remington Magnum, .44 Remington Magnum, .44 Smith & Wesson Special, .45 Automatic30-06 Springfield7.62×39 mm, 8×57 mm, .32 Remington, .35 Remington, .375 Winchester, .38-55 Winchester.30-40 Krag.303 British, .303 Savage, .32 Winchester Special.30-378 Weatherby Magnum8 mm Remington Magnum, .300 Remington Ultra Magnum, .300 Weatherby Magnum, .300 Winchester Magnum, .338 Winchester Magnum, .340 Weatherby Magnum.300 Holland & Holland Magnum8×57 mm, .30-06 Springfield, .30-40 Krag, .375 Winchester, .38-55 Winchester.300 Pegasus.300 Remington Ultra Magnum.300 Remington Short Action Ultra Magnum7 mm-08 Remington.300 Remington Ultra Magnum.30 Remington, .30-30 Winchester, .300 Savage, .308 Winchester, .32 Winchester Special, .357 Remington Maximum, .454 Casull, .480 Ruger.300 Savage.338 Winchester Magnum.300 Weatherby Magnum6.5-300 Weatherby Magnum, .338 Winchester Magnum.300 Winchester Magnum8 mm Mauser round nose magnum, .303 British, .350 Remington Magnum, .375 Winchester, .38-55 Winchester.300 Winchester Short Magnum .32-40 Winchester, .38-40 Winchester, .44-40 Winchester, .44 Remington Magnum, .45 Colt, .454 Casull, .480 Ruger.303 British.30-30 Winchester, .32 Winchester Special.303 Savage.30-30 Winchester, .32 Winchester Special, .32-40 Winchester.308 Marlin Express.38-40 Winchester, .41 Remington Magnum, .44 Remington Magnum, .44 Smith & Wesson Special, .44-40 Winchester.308 Winchester7.62×39 mm, .300 Savage.338 Excalibur.300 Remington Ultra Magnum.338 Lapua Magnum.444 Marlin.338 Remington Ultra Magnum.300 Weatherby Magnum, .35 Whelen.338 Winchester Magnum.375 Winchester, .38-55 Winchester.338-06 A-Square.35 Remington.338-378 Weatherby Magnum.338 Remington Ultra Magnum.340 Weatherby Magnum6.5-300 Weatherby Magnum, .350 Remington Magnum, .375 Winchester, .38-55 Winchester, .416 Taylor Magnum, .444 Marlin.348 Winchester.35 Remington.35 Remington.30-30 Winchester.358 Shooting Times Alaskan7 mm Shooting Times Westerner, .338 Winchester Magnum, 8 mm Remington, .350 Remington Magnum, .358 Norma Magnum, .375 Winchester, .38-55 Winchester, .416 Taylor Magnum.375 H&H Magnum.375 Winchester, .38-55 Winchester.375 Remington Ultra Magnum.375 H&H Magnum, .375 Ruger.375 Weatherby6.5-300 Weatherby Magnum, .416 Taylor Magnum.375 Winchester.38-55 Winchester, .41 Long Colt.378 Weatherby Magnum.375 Remington Ultra Magnum, .416 Taylor Magnum, .444 Marlin, .45-70 Government.38-55 Winchester.375 Winchester, .41 Long Colt, .405 Winchester, 7x30 mm Waters, .30-30 Winchester, .30-40 Krag, .303 British, .375 Winchester, .38-55 Winchester.416 Rigby.300 Remington Ultra Magnum, .338 Remington Ultra Magnum, .416 Remington, .416 Ruger.416 Ruger.444 Marlin, .45–70 Government, .450 Marlin, .500 Smith & Wesson.416 Weatherby Magnum.416 Remington, .416 Rigby, .416 Ruger, .45-70 Government.45-70 Government.454 Casull, .475 Linebaugh, .480 Ruger.458 Lott6.5-300 Weatherby Magnum.460 Weatherby Magnum.458 Winchester

Saboted ammunition and muzzle devices Saboted ammunition uses an "accelerator" (often made of plastic) to form a seal with the barrel to propel a much smaller projectile in a large bore. An example of such ammunition is a saboted light armor penetrator (SLAP), like for example the 12.7×99 mm round designated as M962.

Muzzle devices, like a flash suppressor, muzzle brake, or choke, but especially muzzle brakes, can cause material buildup from copper, lead, etc. upon firing. In particular, firing of saboted ammunition in firearms with muzzle devices can leave behind residue in the muzzle device upon firing, which can cause an increase in barrel and chamber pressure in subsequent firing. The Hard-Target Interdiction sniper manual contains the following warning on page 411: